Safety-valve.



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Patented'l-ar. 18, 1913.

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JOANN'Y LOMBARD, 0F LILLE, FRANCE.

SAFETY-VALVE.

Specification of Letters Patent.

Patented Mar. 18, 1913.

Application led August 8, 1%??11. Serial No. 642,912.

To all fwkom it may concern:

Be it known that I, JOAXXY LOMBARD, citizen of the Republic of France. residing at 3Q Rue de Valenciennes, Lille, Nord, France, have invented new and useful Improvements in Safety-Valves, of which the following isa specification.

The present invention relates to a safety valve for steam generators and other applications, of the typein which a main shut od valve inthe blow oif pipe is combined with a pilot valve the lifting of which determines the actuation of the said main valve. In valves of this type the lifting of the pilot valve when the steam attains an excessive pressure, shuts off communication between the upper face of the main valve and the stealn pressure, and simultaneously places the said upper face in communication with the atmosphere. The main valve then lifts suddenly owing to the pressure of the steam on an annular facing on the bottom of the valve which gives rise to a sudden pressure drop in the steam pressure pipe and subsequent lowering of the pilot valve. This results in continual alternating hammering or knocking of the pilot and main valves.

The present invention has for object to prevent this knocking or hammering which retards the blow off of the steam at excessive pressure, and this object is accomplished by providing at one end of the pilot valve stem a suitable head, formed as adisk or piston, and conducting against one face of the head live steam which passes through a restricted conduit, one end of which is pref-P erably flared and opens into the steam admission passage, and the other end of which opens into one end of the chamber wherein the head on the pilot valve works. The face of the head opposite that which receives the live steam is adapted to be placed in communication with the atmosphere by means of an exhaust port as soon as the main. valve lifts from its seat, the result being that there is' a reduction of pressure on o e side of the head thus enabling the live steam to easily raise the pilot valve and maintain it in elevated position. The steam passing through this restricted conduit always arrives at the pilot valve with some speed and any pressure drop below the pilot is rendered impossible.

Further novel features` will' be subsequently described and pointed out inthe claims. i

' In the accompanying drawings: Figure 1 is a sectional elevation of an Ordinar safety valve of the type referred to, and Figs. 2, 3 and 4, similar views of three examples of the improved safety valve according to this invention.

Fig. 1 of the accompanying drawings shows a combined valve of the usual type.

In a pipe a'tted on the upper part of thechamber df tlie steam generator 1s arranged a balanced pilot valve consisting in a cylinder b on a. portion of which are formed flats b. A pipe c communicates with the atmosphere and is provided with a seating el for the mai valve e which is normally acted upon by the steam on the annular part el of its lower surface and on the whole of its upper surface owing to the passage of the fluid between the flats of the pilot valve and the walls of its pipe.

In Figs. 2, 3 and 4, a denotes as in Fig. l,

the inlet pipe for thesteam coming from the steam chamber of thegenerator, c the blow oipipe in communication with the atmosphere; b the pilot valve and e the main valve for which a seating is fbrmed at d in the pipe c. In the examples of Figs. 2 and 3, the passage arrangementfor the steam act-- ing on the pilot valve is realized bymeans of a conduit with a iiared end `f leading into the pipe a, the other end of the conduit leading into a chamber g in which works ahead or piston b2 formed on the lower end of the pilot valve. The main valve e works in a chamber m of which the upper part is in communication through a port n with the external wall of the part of the pilot valve rod immediately below the seat-ing 123. The surface of the rod is formed with reduced portions such as a series of flats or iiutings o o2 o3 04 of decreasing length, which are successively uncovered when the pilot valve rises. The chamber g is in communication at its upper part through a duct p with a chamber surrounding the lower end of the main valve, and above the seating cl of this latter.

The arrangement works as follows: The live steam coming from the generator on reaching the flared end fis swept into the conduit, and when its'pressure is suiicient, raises the piston b2 of the balanced pilot valve. As soonl as the utings 0 o2 o8 o4 are uncovered above the seating b com- `valve lifts. The lifting of the main valve however, cannot produce in the pipe a a pressure reduction capable of causing knocking of the pilot valve, since the steam 1n this pipe always first encounters the iiaredl end of the conduit f. When the main valve e is raised from its seat, the passage p. serves yto place the chamber g in eommunlcation with the atmosphere, through the exhaust port, and hence the lifting of the valve e causes a corresponding pressure reduction in the upper part of the chamber g, above thepiston b2 of the pilot valve, and tends to increase the lift of this latter. In the example illustrated a progressive lifting of the main valve is moreover assured in the following manner: This valve is hollow,

and its upper wall contains a central taper,-H

ing hole e2 in which fits a rod of similar form g attached to the upper wall of the chamber m. The steam reaches the interior of the hollow valve through narrow passages e e3 and escapes toward the upper part of the chamber m with greater facility as the lift of the valve is greater, so that the back pressure of this shunt flow of steam increases in proportion as the main valve rises, and finally limits this lifting.

In the modification of Fig. 3 the piston b2 instead of fitting steam tight with the walls of the chamber g, consists of a disk having a suitable amount of play between its periphery andthe internal wall of the chamber, the structure -beingl such that a limited amount of clearance -is also provided between Athe stem of the pilot valve and that part vof the valve casing wherein it slides. The duct. p connecting the upper part of the chamber g, and the partwith reducedI diameter of the main valve, may then be omitted. The operation of the arrangement is exactly the same as in the foregoing eX- ample, in that the reduction in pressure produced when the main valve lifts is transmitted to the upper face of the head b2 through the space between the stem of the pilot valve and the casing, whereby the live steam acting against the valve head is enabled to easily raise the pilot valve and hold it in elevated position.

' In the example of Fig. 4, the by-passing of ythe live steam in the pipe awhich leads to the steam chamber of the generator, is obtained by a different method. The rod of the pilot valve I), guided by a sleeve r projecting into the interior of the pipe a is provided at its lower end with a disks of which the edges are preferably curved downward, there being left between the .periphery of the disk and theA walls of the pipe a only a suitably valve seat, a passage providin encounters on its path the disk s and is forced to fiow between it and the wall of the pipe a.

Havingnow described my invention what I claim as new and desire to secure by Letters Patent is 1. In a safety valve, a main valve with its seating in the blow off pipe, a pilot valve having a head at one end of its Stem the lifting of which pilot valve determines the actuation of the main valve, a chamber in which said. head works, a conduit having one end flared and projecting into the admission pipe while the other end opens into the chamber below the head, and means for maintaining the pressure in the chamber above the head the same as that above the main valve seating.

2. A safety valve embodying therein a valve casing having a uid admission port, anexhaust port and a port leading to atmosphere, a pilot valve having a head against which fluid iiowing into said admission port is adapted to impinge, a main valve normally seated over said exhaust port, means adapted, upon actuation of said pilot valve, to place the main valve in communication with atmosphere through said port leading to atmosphere, and means leading from said main valve to said pilot valve whereby one face of the head carried by said pilot valve is placed in communication with the exhaust port when said main valve is placed in communication with atmosphere.

3. In a safety valve, a hollow main valve with its seating in the blow olf pipe, a chamber in which the main valve slides steam tight, narrow passages in the walls of the main valve connecting the space above its seating with the inside of. the said valve, a tapering hole in the top wall of the hollow main valve, a fixed tapering rod passing loosely through the said hole, a pilot valve, a series of progressively lengthenin utings on the pilot valve rod immediately elow the communication between these flutings an the top of the main valve, a chamber 1n which works a head on the end of the pilot valve rod, and a passage having one end flared and projecting into the admission pipe while the plther end opens into the chamber below the 4. In a safety valve, a hollow main valve with its seating in the blow of pipe, a chamber in which the main valve slides steam tight, narrow passages in the walls of the main valve connecting the space above its seating with the inside of the said valve, a tapering hole in the top wall of the hollow main valve, a Xed tapering rod passing loosely through the said hole, a pilot valve, a series of 'progressively lengthening flutings on the pilot rod immediately below thev valve seat, a passage providing communication between these utings andthe top of the main valve, a chamber in which Works a head on the pilot valve rod, a conduit having one end flared and projecting into the admission pipe while the other end 10 opens into the chamber below thehead, and

means for maintaining the pressure in the chamber above the head the same as that l above the main valve seating.

In testimony whereof I have signed my name to this specification in the presence of 15- I-l. C. CoXE. 

